Most modified roofing systems are constructed in two layers: a smooth-surfaced base sheet and a granulated cap sheet. Proper seam and joint application is required at both (or all) layers of the sheets. In roofing systems, all seam joints are overlapped and spread over a period of time so that no adjoining sheet seams align.
Single ply membranes are roofing membranes that are field applied using just one layer of membrane material (either homogeneous or composite) rather than multiple layers. Oftentimes as a result of the overlapping intersection of two, three or four sheets of the membrane, a joint is created.
Current joint patches are generally flat membranes with the butyl or similar adhesive applied to one side with a release liner. Often, when applied to intersecting and overlapping portions of a single ply membrane of different heights, the adhesive does not conform to the vertical step in height thus causing bridging and leaving a void into which water and debris can enter.